This invention relates generally to the field of data storage devices, and more particularly but not by way of limitation to an apparatus and associated method for determining the fly height of a read/write head spatially disposed from a data storage disc.
Modern data storage devices such as disc drives are commonly used in a multitude of computer environments to store large amounts of data in a form that is readily available to a user. Generally, a disc drive has a magnetic disc, or two or more stacked magnetic discs, that are rotated by a motor at high speeds. Each disc has a data storage surface divided into a series of generally concentric data tracks where data is stored in the form of magnetic flux transitions.
A data transfer member such as a magnetic transducer is moved by an actuator to selected positions adjacent the data storage surface to sense the magnetic flux transitions in reading data from the disc, and to transmit electrical signals to induce the magnetic flux transitions in writing data to the disc. The active elements of the data transfer member are supported by suspension structures extending from the actuator. The active elements are maintained a small distance from the data storage surface as the data transfer member flies upon an air bearing comprising an aerodynamic slider portion that is lifted by air currents generated by the spinning discs.
A continuing trend in the industry is toward ever-increasing data storage capacity and processing speed while maintaining or reducing the physical size of the disc drive. Consequently, the data transfer member and supporting structures are continually being miniaturized, data storage densities are continually being increased, and data transfer member fly heights are continually being decreased. The result is an overall increased difficulty in measuring the spatial separation of the data transfer member from the data storage surface. Current optical fly height measurement solutions are not sufficiently accurate below about 0.5 microinches. However, the air bearing dynamic response to a perturbation, such as a physical protuberance, microwaviness of the disc, or patterned data, is inherently more pronounced with ever-decreasing fly height.
It has been determined that by measuring the dynamic response of the slider to a known perturbation, indirect methods can be used to extract a fly height from an empirically determined functional interrelationship between the static fly height and the dynamic response parameters of the slider and its associated structural assembly. It is to these improvements and others as exemplified by the description and appended claims that embodiments of the present invention are directed.
Embodiments of the present invention are directed to a fly height detector apparatus for detecting the fly height of a read/write head spatially disposed from a data storage surface during a data transfer operation, the data storage surface moving relative to the read/write head generating air currents supporting the read/write head at a fly height defining a gap between the read/write head and the data storage surface. The fly height detector apparatus comprises a receiver circuit measuring the frequency of the read/write head; a perturbation deliverable to the gap between the read/write head and the data storage surface to invoke a dynamic response in the read/write head; and a processor circuit responsive to the receiver circuit to derive the fly height in relation to the dynamic response frequency. The processor circuit comprises a memory in which is stored a numerical model describing a functional interrelationship between the fly height and the read/write head frequency.
In one aspect the embodiments of the present invention comprise a method for detecting a fly height of a read/write head spatially disposed from a data storage surface during a data transfer operation. The method comprises moving the data storage surface at a substantially steady speed, generating air currents supporting the read/write head at a substantially static fly height defining a gap between the read/write head and the data storage surface; presenting a perturbation in the gap between the read/write head and the data storage surface, invoking an oscillation in the read/write head; measuring the dynamic response frequency of the read/write head to the perturbation; comparing the dynamic response frequency to a numerical model of fly height in relation to read/write head frequency; and deriving the fly height of the read/write head.
In one aspect the embodiments of the present invention contemplate a disc drive comprising a rotating data storage disc generating air currents sustaining a read/write head at a fly height defining a gap therebetween during data transfer operations, and means for predicting the fly height in relation to the dynamic frequency response of the read/write head to a known perturbation introduced in the gap. In one aspect portions of the disc drive can be replicated to contemplate a bench top fly height tester apparatus.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.